Paging: Difference between revisions
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==Overview== |
==Overview== |
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32 bit x86 processors support a 4GiB virtual address space and current 64 bit processors support a 256TiB virtual address space (with a theoretical maximum of 16EiB). Paging is a system which allows each process to see the full virtual address space, without actually requiring the full amount of physical RAM to be physically installed. In fact, current implementations of x86-64 has a current physical RAM limit of 1TiB and a theoretical limit of 4PiB of physical RAM. |
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Paging is a memory scheme that breaks up memory in groups of pages that are constantly swapped between hard disk and computer. This allows for one to appear as though they have more memory than they actually do. |
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In addition to this, paging introduces the benefit of page-level protection. In this system, user-level (ring 3) processes can only see and modify data which is paged in to their own address space, providing hardware isolation. System pages are also protected from user processes. |
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Once an Operating System has paging, it can also make use of other benefits and workarounds, such as linear framebuffer simulation for memory-mapped IO and paging out to disk, where disk storage space is used to free up physical RAM. |
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==MMU== |
==MMU== |
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